1. Field of the Invention
The present invention relates to a sheet feeding device for feeding a sheet to a predetermined target, and an image forming apparatus having the sheet feeding device.
2. Description of the Related Art
An image forming apparatus, such as a printer, copy machine and facsimile, has an image forming section for forming an image on a sheet and a sheet feeding device for feeding the sheet from a sheet storage section to the image forming section along a sheet conveying path. The sheet feeding device has a pair of sheet feeding rollers for sending the sheet to the sheet conveying path, and a pair of conveying rollers disposed on the downstream side of the sheet feeding rollers in the sheet conveying path and conveying the sheet to the further downstream side of the sheet conveying path.
It has been known that this sheet feeding device having the configuration mentioned above causes noise, so-called “paper slip noise.” This noise occurs as follows. The sheet is conveyed while being stretched between the sheet feeding roller pair and the conveying roller pair by having one end of the sheet in a sheet conveying direction sandwiched between the pair of conveying rollers and the other end between the pair of sheet feeding rollers. When a vibration generated from the sheet feeding device propagates to the sheet while the sheet is conveyed in such a condition, the sheet vibrates. As a result, the paper slip noise occurs. The paper slip noise is unpleasant for a user.
A first technology has been known as the countermeasures for reducing the paper slip noise. In a sheet feeding device of the first technology, a roller that is capable of coming into contact with a sheet passing through a sheet feeding roller pair is provided on the downstream side of the sheet feeding roller pair in the sheet conveying direction. This roller prevents the abovementioned vibration by coming into contact with the vibrating paper. In this manner, the occurrence of the paper slip noise can be reduced.
The sheet feeding device of the first technology further includes a guide plate that is disposed along the sheet conveying path in the downstream of the sheet feeding roller pair in the sheet conveying direction, and a resonance chamber (so-called Helmholtz resonator) that has a predetermined space formed on the guide plate. The size of the Helmholtz resonator is set as to have a predetermined frequency characteristic corresponding to the frequency of the paper slip noise, in order to prevent the occurrence of the paper noise slip.
Although the sheet feeding device of the first technology reduces the occurrence of the paper slip noise by disposing the roller and the Helmholtz resonator along the sheet conveying path, the increase in the number of parts by adopting the roller and the Helmholtz resonator, the subsequent increase in the cost, and the complexity of the structure of the device are inevitable.